| Title: | Mass fluxes of dissolved arsenic discharging to the Meghna River are sufficient to account for the mass of arsenic in riverbank sediments |
| Author(s): | Huang Y; Knappett PSK; Berube M; Datta S; Cardenas MB; Rhodes KA; Dimova NT; Choudhury I; Ahmed KM; van Geen A; |
| Address: | "Dept. Geology & Geophysics, Texas A&M University, College Station, TX 77843, USA. Electronic address: huangyibin123@tamu.edu. Dept. Geology & Geophysics, Texas A&M University, College Station, TX 77843, USA. Dept. Geological Sciences, Kansa State University, Manhattan, KS 66506, USA. Electronic address: berubem@ksu.edu. Dept. Geological Sciences, The University of Texas, San Antonio, TX 78249, USA. Electronic address: Saugata.Datta@utsa.edu. Dept. Geological Sciences, The University of Texas, Austin, TX 78712, USA. Electronic address: cardenas@jsg.utexas.edu. Water Management and Hydrological Sciences Program, Texas A&M University, College Station, TX 77843, USA. Dept. Geological Sciences, University of Alabama, Tuscaloosa, AL 35487, USA. Electronic address: ntdimova@ua.edu. Dept. Geology, University of Dhaka, Dhaka 1000, Bangladesh. Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA. Electronic address: avangeen@ldeo.columbia.edu" |
| DOI: | 10.1016/j.jconhyd.2022.104068 |
| ISSN/ISBN: | 1873-6009 (Electronic) 0169-7722 (Linking) |
| Abstract: | "Shallow (<30 m) reducing groundwater commonly contains abundant dissolved arsenic (As) in Bangladesh. We hypothesize that dissolved As in iron (Fe)-rich groundwater discharging to rivers is trapped onto Fe(III)-oxyhydroxides which precipitate in shallow riverbank sediments under the influence of tidal fluctuations. Therefore, the goal of this study is to compare the calculated mass of sediment-bound As that would be sequestered from dissolved groundwater As that discharges through riverbanks of the Meghna River to the observed mass of As trapped within riverbank sediments. To calculate groundwater discharge, a Boussinesq aquifer analytical groundwater flow model was developed and constrained by cyclical seasonal fluctuations in hydraulic heads and river stages observed at three sites along a 13 km reach in central Bangladesh. At all sites, groundwater discharges to the river year-round but most of it passes through an intertidal zone created by ocean tides propagating upstream from the Bay of Bengal in the dry season. The annualized groundwater discharge per unit width at the three sites ranges from 173 to 891 m(2)/yr (average 540 m(2)/yr). Assuming that riverbanks have been stable since the Brahmaputra River avulsed far away from this area 200 years ago and dissolved As is completely trapped within riverbank sediments, the mass of accumulated sediment As can be calculated by multiplying groundwater discharge by ambient aquifer As concentrations measured in 1969 wells. Across all sites, the range of calculated sediment As concentrations in the riverbank is 78-849 mg/kg, which is higher than the observed concentrations (17-599 mg/kg). This discovery supports the hypothesis that the dissolved As in groundwater discharge to the river is sufficient to account for the observed buried deposits of As along riverbanks" |
| Keywords: | "*Arsenic/analysis Rivers Geologic Sediments Ferric Compounds *Water Pollutants, Chemical/analysis *Groundwater Environmental Monitoring Arsenic Groundwater discharge Permeable natural reactive barrier;" |
| Notes: | "MedlineHuang, Yibin Knappett, Peter S K Berube, Michelle Datta, Saugata Cardenas, M Bayani Rhodes, Kimberly A Dimova, Natasha T Choudhury, Imtiaz Ahmed, Kazi M van Geen, Alexander eng P42 ES010349/ES/NIEHS NIH HHS/ Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. Netherlands 2022/09/16 J Contam Hydrol. 2022 Dec; 251:104068. doi: 10.1016/j.jconhyd.2022.104068. Epub 2022 Sep 2" |
